Neutral mechanical alignment: a requirement for successful TKA: affirms

Area of Science:

• Orthopedic Surgery
• Biomechanics
• Biomedical Engineering

Background:

• Neutral mechanical axis is a traditional goal in total knee arthroplasty (TKA).
• Coronal malalignment, especially varus, is linked to increased strain, higher failure rates, and poorer outcomes.
• Technological advancements like navigation and 3D imaging enhance surgical precision in TKA.

Purpose of the Study:

• To re-evaluate the importance of neutral alignment in TKA.
• To discuss the implications of recent studies challenging the alignment safe zone.
• To reaffirm the validity of neutral alignment and classic bone cuts for successful TKA outcomes.

Main Methods:

• Review of biomechanical, finite element, and clinical studies.
• Analysis of recent literature on TKA survivorship and alignment.
• Discussion of surgical technology's impact on alignment precision.

Main Results:

• Recent studies show no difference in survivorship for malaligned TKAs, challenging the alignment safe zone concept.
• Despite technological improvements, the human factor necessitates a safe margin for error.
• Evidence supporting neutral mechanical axis and 5°-7° valgus anatomic alignment is stronger than for alternative targets.

Conclusions:

• Neutral alignment and classic bone cuts remain valid and important for successful TKA.
• While TKA kinematics are better understood, broad alignment targets may not offer significant benefit as a dichotomous variable.
• The primary goal of TKA is a durable, well-functioning joint, prioritizing function over replicating native anatomy.